pkgsrc binary package retention timeline

[Justin C. Sherrill]

We currently have a large quantity of binary pkgsrc packages on
avalon.dragonflybsd.org:

drwxr-xr-x  1 root  wheel   0 Jun  3 10:48 DragonFly-1.12
drwxr-xr-x  1 root  wheel   0 Jun  4 05:49 DragonFly-2.0
drwxr-xr-x  1 root  wheel   0 Jun 14 03:10 DragonFly-1.10.1
drwxr-xr-x  1 root  wheel   0 Jun 14 18:05 DragonFly-2.2
drwxr-xr-x  1 root  wheel   0 Jul 13 15:09 DragonFly-2.3.1

(I'm not showing directories that are links to these, to cover all version
numbers.)  Each one of these directories may hold multiple quarterly
releases of pkgsrc, plus current builds.

In an effort to keep this from becoming a huge archive, I plan to keep the
current release's packages and the last release's packages, plus any
packages built for HEAD due to compatibility changes.  This means that
we'd have only 2.0 packages, 2.2 packages, and 2.3.1+ packages.

Once 2.4 comes out, we'd have only 2.2 and 2.4 packages, plus 2.5 if
something happened that required that, like another libc change. 
Otherwise, a link from 2.5 to the 2.4 packages would work.

This gives us a year of available binaries for any given release,
especially once I have this more automated.  Any objections to this plan? 
I figure this won't be a problem for anyone running a 2.x system.